[pm/metrics] fix test on user 10

InstallRequest.mUid is actually appId. Renaming to reflect that. Compute
the actual UID in the metrics class.

RemovedInfo.mUid is also appId, except in one place where it's used
outside the installation flow. That will be fixed in a separate CL.

BUG: 262710779
Test: atest com.android.cts.packagemanager.stats.host.PackageInstallationSessionReportedStatsTests
Change-Id: I6284f381b5760d14b4913ace5183a5b6f32db9b4